not at all

Từ điển Oxford Advanced Learner 8th

▪ I. ˌnot at ˈall idiom
used as a polite reply to an expression of thanks
• ‘Thanks very much for your help.’ ‘Not at all, it was a pleasure.’
Main entry: ↑all_idiom
 
▪ II. ˌnot at ˈall idiom
used to politely accept thanks or to agree to sth
• ‘Thanks a lot.’ ‘Not at all.’
• ‘Will it bother you if I smoke?’ ‘Not at all.’
Main entry: ↑not_idiom
 
▪ III. (not) at all idiom
in any way; to any degree
• I didn't enjoy it at all.
Main entry: ↑all_idiom